Solved Remote Clients- Intermittent Audio

[varunbhagaloo]

I know the issue of call audio has been posted multiple times in the forum, I've tried everything I can think of but still getting an issue.

I have 3CX set up locally hosted at Site A with 14 extensions (Alll Fanvil extensions)
I have 2 Fanvil X3SG set up remotely at Site B. They connect to Site A via STUN. Site A has no issues whatsoever
I have 2 Fanvil X3SG set up remotely at Site C. They connect to Site A via STUN.

Site C has issues daily with audio dropping on both extensions.
Calls can be sent and received fine, but with no audio on either end. Sometimes the system works perfectly, then randomly both extensions would experience complete audio loss at the same time.
The customer has the 3CX app installed on Android running off the WiFi (same network as the desk phones), the app works perfectly all day long, regardless if the desk phones are giving issues or not.
When the audio dropping issue occurs, the 'signal' indicator on the phones drops to 1 bar. The phones are all hardwired to the router.

I've set one extension (115) to SIP port 5070 and RTP to 14000-14019
The other extension (116) is set to SIP port 5071 and RTP to 14020-14039
Both extensions have local static IP's assigned, and relevant ports forwarded on the router.
The router in Site C is Linksys E900, SIP ALG is turned off.

The routers in site A and B are both Ubiquiti EdgeRouter X's
All 3 sites are served by the same ISP and have static public IPs.

At this point, I would think the issue is either ISP or router related? I even went so far as to factory reset the linksys router and reconfigure from scratch, but this had absolutely no effect on the behavior.

 

[Alphabetic]

Have you tried turning on "PBX Delivers Audio" under each extension > Options?

 

[varunbhagaloo]

Have you tried turning on "PBX Delivers Audio" under each extension > Options?

View attachment 25844

Yep! If this is turned off there is not audio at all.

 

[Alphabetic]

Is the firewall on the PBX passing?

It's likely a routing issue on either side and I would consider sticking in a Pi to use as an SBC as a cheaper alternative to a replacement router.

https://www.3cx.com/docs/installing-pbx-raspberry-pi/

https://www.3cx.com/docs/3cx-tunnel-session-border-controller/

 

[varunbhagaloo]

Yep the firewall test on the PBX has passed.
I've installed multiple 3CX instances with 2 remote extensions on a site, and never needed a SBC for just 2 remote extensions.
I'm SURE it's a routing issue, specifically this cheapo Linksys being the cause. Are audio issues common with linksys routers?

 

[Alphabetic]

Yep the firewall test on the PBX has passed.
I've installed multiple 3CX instances with 2 remote extensions on a site, and never needed a SBC for just 2 remote extensions.
I'm SURE it's a routing issue, specifically this cheapo Linksys being the cause. Are audio issues common with linksys routers?

Ok, so you suspect its the router and you've factory reset it to no avail...

next step firmware update and then replace.

 

[varunbhagaloo]

Firmware is already at the latest.

My thing is, if the Android app works flawlessly on the same network, why doesn't the desk phones?
Does the App use a different method to connect to the PBX server?

 

[Alphabetic]

Firmware is already at the latest.

My thing is, if the Android app works flawlessly on the same network, why doesn't the desk phones?
Does the App use a different method to connect to the PBX server?

The mobile apps use the SBC tunnel on 5090

 

[ChrisC_3CX]

As @kieferschild mentioned, the 3CX mobile apps operate in a very different manner and also utilize the 3CX Tunnel meaning that media and SIP signaling traffic is encapsulated.

From your description it does sound like you setup STUN correctly but at the same time everything does seem to suggest it's the router/firewall itself or it's configuration causing the issue. I understand wanting to avoid using an extra device just to host the 3CX SBC but it may be worth considering since the time spent troubleshooting this issue might not be worth it in the end. Especially since the SBC offers things like extra security (due to 3CX tunnel), no need for firewall configuration on the remote site, easy PnP provisioning and an overall better management experience.

 

[varunbhagaloo]

Thanks Chris. I may very well need to invest in that SBC. I should have an old PI 3 laying around I can use. Even if the customer doesn't want to pay for additional hardware it'll be worth it to save my own reputation.

 

[varunbhagaloo]

I installed an SBC on Wednesday, reset and provisioned both handsets to point to the SBC, but users are still reporting that the phones are dropping audio. I'm wondering if it's an issue with the ISP in that area.
Is there any tool that I can run for a period of time to determine if the internet connection itself is dropping packets randomly? Regular online speedtests run fine (100mbps, <10ms ping, <5ms jitter).

 

[Alphabetic]

Are they able to replicate it?

You're going to have to start some wireshark captures to see what is happening with the audio.

You should start a trace on the SBC and also the PBX. But, my advice would be to get them to make test phone calls until it happens again otherwise you'll have a lot of data to go through.

Once you've got both captures, you should check to see if the audio is passing through the SBC and hitting the PBX.

The audio should be encapsulated inside the tunnel so if audio is being dropped, id expect the tunnel to drop too.

Have you tried the possibility that the handsets are faulty?

 

[varunbhagaloo]

I don't think the handsets are faulty, they both drop audio at the exact same time, then work properly again at the same time. So it's definitely something network related.

I'll try setting up some captures..

 

[ChrisC_3CX]

You could also try disabling "PBX Delivers audio" to narrow this down a bit. Disable it for both extensions and also disable call recording for both extensions. Then, when the issue occurs and you can replicate it at will, make a call between two IP Phones behind that same SBC. The audio for this call should stay in that LAN, if the audio is ok for this call but you then still have issues by calling *777 for an echo test, then you'll know that the issue is indeed between the remote site and the PBX.

 

[varunbhagaloo]

Thanks Chris, I'lll try that as well.

 

[varunbhagaloo]

So this issue seems to have been sorted by just installing the SBC. I did a visit last week, and the client said the phones have been working well, save for some minor audio issues for the first call of the morning. I'm not sure why the issue wasn't immediately solved when the SBC was first installed, but it seems to have fixed itself on its own.

Thanks all for the assistance!

 

[ChrisC_3CX]

You're very welcome! just glad to hear you managed to get this sorted!

Just make sure you've removed any remnant firewall configurations implemented to accommodate for STUN on the remote site. Remember, the 3CX SBC required no port forwarding on it's end.

Feel free to start a new thread should you need anything else!